There's more information in a stereo signal than just the levels of the left and right speakers. fielder attempts to show you what your brain actually hears:
a continuous stereo field between two speakers comprised of both direction and breadth.

Visualizing the stereo image can be helpful to sound designers and engineers during a mixing or post-production process, can help emphasize awareness of stereo perception, and is just fun to watch while listening!

fielder calculates vectors representing the amplitude and stereo direction of the audio signal at a given slice of time. These vectors can be displayed in 3 different modes.